Our purpose is to determine the feasibility of using spring-loaded devices to assist with locomotor therapy (LT) for patients with incomplete spinal cord injuries (iSCI). LT involves partial weight-supported treadmill walking with assisted leg motions. Intensive, manually assisted LT by physical therapists is proven effective but is exhausting for therapists and expensive due to high labor costs. Robotic LT reduces labor costs but requires very expensive machines and is not as effective as manual LT. Thus, many patients do not receive optimal LT. Recently, spring-loaded devices have been developed that assist with leg swing and forward propulsion in healthy subjects. These devices apply forward pulling, Leg Swing Assist (LSA) forces to each foot or Forward Propulsion Assist (FPA) forces to the waist. Our overall goal is to adapt these spring-loaded assist devices to help patients learn to walk again. Our specific aim is to identify the optimal mechanical properties for the spring-loaded devices (i.e. initial assist force, maximum assist force, stiffness of spring elements). Optimal is defined as the conditions that mostly closely reproduce the kinematics, ground reaction forces and EMG patterns measured during manual LT. Our hypotheses are: 1. The optimal leg swing assist force pattern will rapidly transition from zero during the first half of stance phase to reach a maximum just prior to swing initiation and then rapidly decline to zero after mid-swing. and 2. A nearly constant, forward propulsion assist force applied at the waist is optimal and allows for greater weight bearing and more natural gait. Carts equipped with leg swing and forward propulsion assist apparatus will be constructed and tested on iSCI patients. These data will guide prototype designs under a Phase II SBIR grant. These simple spring-loaded assist devices offer great promise for helping patients with gait disorders regain their ability to walk independently. This research will explore the feasibility of using simple, spring-loaded devices to help patients with gait disorders re-learn how to walk during treadmill locomotor therapy. The devices replace the manual assistance with leg movements currently provided by physical therapists. These devices may allow patients to receive more extensive and thus effective treadmill walking therapy at a greatly reduced financial cost. [unreadable] [unreadable]